Field
Aspects of the present invention generally relate to an apparatus for performing tomography on an object using radiation, and in particular, to an apparatus for performing breast tomography.
Description of the Related Art
In tomography, portions put on an image pickup area often have different cross-sectional shapes according to objects. In particular, in a tomography apparatus for breast inspection, when a dose of radiation to be delivered to photograph a portion having a large cross-sectional shape is increased to uniform the dose of radiation transmitted through the object regardless of the shape of the object, a portion having a small cross-sectional shape is exposed to excessive radiation. Further radiation has a difference in radiation quality due to beam hardening effect according to a transmission length of the object, and the difference in radiation quality causes deterioration in quality of a reconstructed image.
For reduction in dose of radiation to which the object is exposed and uniform dose distribution or radiation quality, as described above, a filter called wedge filter is known which controls dose distribution or radiation quality. The wedge filter is a filter provided between a radiation generator and the object. As the wedge filter, a filter called a bowtie filter is known. The bowtie filter has a shape having a thickness small at the center corresponding to a major part of the object and large at the peripheral part corresponding to a minor part of the object. Japanese Patent Application Laid-Open No. 2005-034173 discloses a technique for obtaining an X-ray intensity distribution desirably adjusted using an X-ray distribution adjusting filter provided with a bellows-shaped movable portion.
However, in Japanese Patent Application Laid-Open No. 2005-034173, the filter is complicatedly adjusted to be matched with the shape of the object. Accordingly, the filter is less matched with the shape of the object, and an unnecessary dose of radiation to which the object is exposed, is insufficiently reduced.